Cystic fibrosis
Shortened Lung Clearance Index is a repeatable and sensitive test in children and adults with cystic fibrosis David Hannon,1 Judy M Bradley,2 Ian Bradbury,2 Nicholas Bell,3 J Stuart Elborn,1 Katherine O’Neill1
To cite: Hannon D, Bradley JM, Bradbury I, et al. Shortened Lung Clearance Index is a repeatable and sensitive test in children and adults with cystic fibrosis. BMJ Open Resp Res 2014;1: e000031. doi:10.1136/ bmjresp-2014-000031
▸ Additional material is available. To view please visit the journal (http://dx.doi.org/ 10.1136/bmjresp-2014000031) JSE and KO are Joint senior authors. Received 12 March 2014 Revised 27 June 2014 Accepted 30 June 2014
1
Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University Belfast, Belfast, UK 2 Centre for Health and Rehabilitation Technologies (CHART), University of Ulster, Belfast, UK 3 Respiratory Medicine Department, Bristol Adult Cystic Fibrosis Centre, Bristol Royal Infirmary, University Hospitals Bristol, Bristol, UK Correspondence to Professor J Stuart Elborn; [email protected]
ABSTRACT Background: Lung clearance index (LCI) derived from sulfur hexafluoride (SF6) multiple breath washout (MBW) is a sensitive measure of lung disease in people with cystic fibrosis (CF). However, it can be time-consuming, limiting its use clinically. Aim: To compare the repeatability, sensitivity and test duration of LCI derived from washout to 1/30th (LCI1/30), 1/20th (LCI1/20) and 1/10th (LCI1/10) to ‘standard’ LCI derived from washout to 1/40th initial concentration (LCI1/40). Methods: Triplicate MBW test results from 30 clinically stable people with CF and 30 healthy controls were analysed retrospectively. MBW tests were performed using 0.2% SF6 and a modified Innocor device. All LCI end points were calculated using SimpleWashout software. Repeatability was assessed using coefficient of variation (CV%). The proportion of people with CF with and without abnormal LCI and forced expiratory volume in 1 s (FEV1) % predicted was compared. Receiver operating characteristic (ROC) curve statistics were calculated. Test duration of all LCI end points was compared using paired t tests. Results: In people with CF, LCI1/40 CV% (p=0.16), LCI1/ 30 CV%, (p=0.53), LCI1/20 CV% (p=0.14) and LCI1/10 CV % (p=0.25) was not significantly different to controls. The sensitivity of LCI1/40, LCI1/30 and LCI1/20 to the presence of CF was equal (67%). The sensitivity of LCI1/ 10 and FEV1% predicted was lower (53% and 47% respectively). Area under the ROC curve (95% CI) for LCI1/40, LCI1/30, LCI1/20, LCI1/10 and FEV1% predicted was 0.89 (0.80 to 0.97), 0.87 (0.77 to 0.96), 0.87 (0.78 to 0.96), 0.83 (0.72 to 0.94) and 0.73 (0.60 to 0.86), respectively. Test duration of LCI1/30, LCI1/20 and LCI1/10 was significantly shorter compared with the test duration of LCI1/40 in people with CF ( p
Shortened Lung Clearance Index is a repeatable and sensitive test in children and adults with cystic fibrosis David Hannon,1 Judy M Bradley,2 Ian Bradbury,2 Nicholas Bell,3 J Stuart Elborn,1 Katherine O’Neill1
To cite: Hannon D, Bradley JM, Bradbury I, et al. Shortened Lung Clearance Index is a repeatable and sensitive test in children and adults with cystic fibrosis. BMJ Open Resp Res 2014;1: e000031. doi:10.1136/ bmjresp-2014-000031
▸ Additional material is available. To view please visit the journal (http://dx.doi.org/ 10.1136/bmjresp-2014000031) JSE and KO are Joint senior authors. Received 12 March 2014 Revised 27 June 2014 Accepted 30 June 2014
1
Centre for Infection and Immunity, School of Medicine, Dentistry and Biomedical Sciences, Queen’s University Belfast, Belfast, UK 2 Centre for Health and Rehabilitation Technologies (CHART), University of Ulster, Belfast, UK 3 Respiratory Medicine Department, Bristol Adult Cystic Fibrosis Centre, Bristol Royal Infirmary, University Hospitals Bristol, Bristol, UK Correspondence to Professor J Stuart Elborn; [email protected]
ABSTRACT Background: Lung clearance index (LCI) derived from sulfur hexafluoride (SF6) multiple breath washout (MBW) is a sensitive measure of lung disease in people with cystic fibrosis (CF). However, it can be time-consuming, limiting its use clinically. Aim: To compare the repeatability, sensitivity and test duration of LCI derived from washout to 1/30th (LCI1/30), 1/20th (LCI1/20) and 1/10th (LCI1/10) to ‘standard’ LCI derived from washout to 1/40th initial concentration (LCI1/40). Methods: Triplicate MBW test results from 30 clinically stable people with CF and 30 healthy controls were analysed retrospectively. MBW tests were performed using 0.2% SF6 and a modified Innocor device. All LCI end points were calculated using SimpleWashout software. Repeatability was assessed using coefficient of variation (CV%). The proportion of people with CF with and without abnormal LCI and forced expiratory volume in 1 s (FEV1) % predicted was compared. Receiver operating characteristic (ROC) curve statistics were calculated. Test duration of all LCI end points was compared using paired t tests. Results: In people with CF, LCI1/40 CV% (p=0.16), LCI1/ 30 CV%, (p=0.53), LCI1/20 CV% (p=0.14) and LCI1/10 CV % (p=0.25) was not significantly different to controls. The sensitivity of LCI1/40, LCI1/30 and LCI1/20 to the presence of CF was equal (67%). The sensitivity of LCI1/ 10 and FEV1% predicted was lower (53% and 47% respectively). Area under the ROC curve (95% CI) for LCI1/40, LCI1/30, LCI1/20, LCI1/10 and FEV1% predicted was 0.89 (0.80 to 0.97), 0.87 (0.77 to 0.96), 0.87 (0.78 to 0.96), 0.83 (0.72 to 0.94) and 0.73 (0.60 to 0.86), respectively. Test duration of LCI1/30, LCI1/20 and LCI1/10 was significantly shorter compared with the test duration of LCI1/40 in people with CF ( p
